We have already seen how the first process that lives from boot to the shutdown of the OS is called init or init.d since it's a daemon. This process is responsible for handling the other daemons, and stores its configuration in the /etc/init.d directory.
Each Linux distribution uses its own version of the daemon control process, like upstart for Chrome OS or systemd in Arch Linux. They all serve the same purpose and have similar behavior.
Each daemon has a control script or application that resides inside /etc/init.d and should be able to interpret a series of commands as first arguments, such as status, start, stop, and restart. In most cases, the init.d file is a script that executes a switch on the argument and behaves accordingly.